- Joined
- Jan 16, 2019
- Messages
- 82
- Karma
- 17
- Gear owned
- Tascam Ampex Mechlabor
Guys,
I sold my Tascam 122MKIII, and before the final calibration, I realized quite some EMI noise coming through the channels. I planned to place decoupling capacitors earlier anyaway, so I decided to do so now. I put 0,1uF/50V ceramic capacitors on each opamps power rails, meanwile checking the results as I progressed, and it was promising. When I tested the machine with playing some music, an awfull cracking noise came through one of the channels, the VU meter danced madly, then I lost one channel. After testing the circuits I realised that I lost one repro channel (dual JFET+EQ opamp, circled on the pic). I suspect that the opamp got instabile and blew up..
I double checked each and every soldering of the newly added capacitors, all seems ok, and I have no idea, what caused the fault. I soldered the capacitors on the wired side of the PCB. It would be good to know before I replace the opamp and the dual JFET which also seems to go faulty.
I sold my Tascam 122MKIII, and before the final calibration, I realized quite some EMI noise coming through the channels. I planned to place decoupling capacitors earlier anyaway, so I decided to do so now. I put 0,1uF/50V ceramic capacitors on each opamps power rails, meanwile checking the results as I progressed, and it was promising. When I tested the machine with playing some music, an awfull cracking noise came through one of the channels, the VU meter danced madly, then I lost one channel. After testing the circuits I realised that I lost one repro channel (dual JFET+EQ opamp, circled on the pic). I suspect that the opamp got instabile and blew up..
I double checked each and every soldering of the newly added capacitors, all seems ok, and I have no idea, what caused the fault. I soldered the capacitors on the wired side of the PCB. It would be good to know before I replace the opamp and the dual JFET which also seems to go faulty.
